Custom Gym Environment Registration Error - Invalid ID Format

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1

I’m trying to build my own custom environment using OpenAI Gym on Ubuntu. I followed a tutorial and managed to complete most steps including running the pip install command. However, when I try to create the environment using gym.make(), I’m getting a registration error.

Here’s my project structure:

customEnv/
  README.md
  setup.py
  customEnv/
    __init__.py
    envs/
      __init__.py
      customEnv.py

My setup.py looks like this:

from setuptools import setup

setup(name='customEnv',
      version='0.0.1',
      install_requires=['gym']
)

In the main init.py file:

from gym.envs.registration import register

register(
    id='customEnv',
    entry_point='customEnv.envs:customEnv',
)

The envs/init.py contains:

from customEnv.envs.customEnv import customEnv

The installation works fine, but when I try to use it:

import numpy as np
import gym
import customEnv

env = gym.make('customEnv')

I get this error: gym.error.Error: Attempted to register malformed environment ID: customEnv. (Currently all IDs must be of the form ^(?:[\w:-]+\/)?([\w:.-]+)-v(\d+)$.)

What am I doing wrong with the environment ID format?

2

The error’s pretty straightforward - your environment ID needs a version number. OpenAI Gym requires IDs to end with -v0, -v1, etc. I hit this exact same problem when I started making custom environments. Change your registration from id='customEnv' to id='customEnv-v0' in your main __init__.py file. Then use env = gym.make('customEnv-v0') instead of just 'customEnv'. The versioning lets you maintain different versions of your environment - handy when you want to update while keeping backward compatibility. Took me hours to figure this out when I first ran into it.

3

Had the same issue last year with my first custom environment. That regex pattern shows exactly what Gym wants - your ID needs a version suffix like -v0 or -v1. Don’t just add the version number though. Check your entry point path too. Should probably be entry_point='customEnv.envs:CustomEnv' if you’re following Python naming conventions. Also make sure your class inherits from gym.Env and implements step(), reset(), render(), plus defines action_space and observation_space. Sometimes the registration error hides other problems with your environment class.

4

Same thing happened to me when I upgraded from an older Gym version. They made versioning stricter around 0.21+. Along with adding -v0 to your ID, try being more explicit with your entry point - use the full class name like 'customEnv.envs.customEnv:CustomEnv' (assuming your class is CustomEnv). Also check that pip install actually worked by running pip list to confirm your package shows up. Sometimes it fails silently and you won’t see the registration error until runtime. What helped me debug this was throwing a print statement in the init.py registration block to make sure it’s running when you import.

5

yeah, the ID thing’s annoying but you need that -v0 suffix. your naming’s a bit messy tho - customEnv everywhere gets confusing. I’d rename the class to CustomEnv (capital C) and use ‘custom-env-v0’ for the ID. also, make sure your pip install -e actually worked in editable mode.